Most digital video transmission bases new pictures on one or more previously transmitted pictures, known as “reference pictures.” If a transmission error causes a flaw in a picture, continued use of that picture as a reference will tend to result in flawed pictures. Thus, flaws could exist indefinitely. In other words, errors propagate through time.
Typically, the decoder will know when an error has occurred and can send a message to the encoder informing it of the transmission error. The encoder responds by sending a picture that does not depend on any other picture, often called a “key” picture or “Intra” picture. An Intra picture will generally need many more bits than the normal (“Inter”) pictures for equivalent quality. To avoid a long delay before the Intra picture is displayed, it often is sent at a lower quality. This results in a blurrier picture. Subsequent Inter pictures based on this Intra picture will typically become progressively sharper, unless there is a lot of motion or another transmission error occurs.
On lossy networks, such as the Internet, it is common for a transmission error to occur every few seconds. Using the typical procedures implemented by most encoder/decoder systems, this means that the picture gets blurry every few seconds as a new Intra picture is transmitted. Thus, it would be desirable to provide a mechanism by which this intermittent blurriness can be avoided.
While the subject matter of the present disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. The figures and written description are not intended to limit the scope of the inventive concepts in any manner. Rather, the figures and written description are provided to illustrate the inventive concepts to a person skilled in the art by reference to particular embodiments, as required by 35 U.S.C. §112.